I don't have one favourite song and after all no favourite album. I almost never buy albums, but rather pick single songs I like.
Here a short list of some amazing songs, though:
Maldito duende - Héroes del Silencio
If Tomorrow Never Shows - Any Given Day
Stop Dimentica - Tiziano Ferro
Roméo kiffe Juliette - Grand Corps Malade
Hoy vivo por ti - Tierra Santa
Entre dos tierras - Héroes del Silencio
...And an awful lot by Nirvana!